1. Field of the Invention
The present invention relates to on-line measurement systems, an in particular to automating the setup of such systems for the measurement of extruded products using an ultrasonic gauge.
2. Related Art
Ultrasonics provides an ideal mechanism to monitor extruded products where information about internal dimensions and possible defects is desired. These extruded products can be made of one or more layers of different materials. These different layers of material may serve different purposes in the product, and they may have a wide range in price. The manufacturer wishes to control the extrusion process to always exceed the minimum performance requirements for the product, while also using the minimum amount of material. If they have real time information about the product, the extrusion process can be controlled to produce the desired result.
An ultrasonic signal, or impulse is transmitted to the product by way of a transducer. This impulse will be injected into the extruded material by way of way of a coupling medium, which is often water. The acoustic properties of the materials differ from one another, and from the medium through with they are moving, creating interface regions that can be detected. At such an interface, some of the ultrasonic signal will be reflected back toward its point of origin. This reflected signal can be detected by the same transducer that created the original signal, or by another. The round trip time between when the impulse was created and when the reflected signal is detected is multiplied by the speed of sound in the material to get the thickness of the layer. By measuring the thickness of every layer, the total thickness of the product at that point can be calculated. When this measurement is repeated at several points around the product, a more detailed understanding of the extrusion process can be created. Additional measurements, such as the concentricity of the layers can be determined, adding additional value to the measurement and control system.
These measurement and control systems have existed for some time and have been progressing from Analog Measurement Systems to Digital Measurement System. The older analog systems require a lot of experience to set up and run accurately. Each time the product being made is changed, a new setup must be made. This setup involves the operator looking at the raw signals, and using their experience to adjust the system to get a good measurement. This process relies heavily on the experience of the operator, and requires that more experienced personnel are employed to manufacture the products. This is also time consuming, and while the system is being adjusted, the extruder is making product that will have to be scrapped because it is of unknown quality. This can be very expensive, depending on the type of product being manufactured.
The newer digital measurement systems have introduced some automation to the set up of these extrusion control systems. They often will be able to set up most of the required parameters automatically, when used with thick, single layer extrusions. These types of products generate a simple electrical signal, which is relatively easy for the computer to interpret. They still have difficulty with multiple layered products, especially if they include thin layers, which require the operator to manually adjust some of the parameters. While better than the older analog systems, they still are not user friendly, and rely too heavily on the experience of the operator to get an accurate reading.
It is an object of the invention to improve on-line measurement systems for products formed in a continuous manner.
It is another object to improve on-line wall thickness and concentricity measurement for product formed in a continuous manner.
It is another object to simplify operation of on-line measurement of product formed in a continuous manner.
It is yet another object to increase the accuracy of on-line measurement for product formed in a continuous manner.
It is yet another object to provide a more robust on-line measurement system for product formed in a continuous manner.
Still another object is to reduce waste of product by improving on-line measurement system for product formed in a continuous manner
Accordingly, the invention is directed to an improvement in an on-line measurement system for product formed in a continuous manner. The improvement includes a device for receiving a first waveform signal indicative of a presence of a first characteristic of the product and a second waveform signal indicative of a presence of a second characteristic of the product. A computer based device having phase shifting software is provided for shifting phase of each of the first waveform signal and the second waveform signal a predetermined amount to produce a respective first transformed waveform signal and a second transformed waveform signal. Further, software is provided in the computer based device for combining the first waveform signal and the first transformed waveform signal in manner to produce a first rectified waveform having an increasingly defined peak and for combining the second waveform signal and the second transformed waveform signal in manner to produce a second rectified waveform having an increasingly defined peak, wherein the peaks are useful in the in-line measurement system for defining a third characteristic of the product. A method employing the invention is also provided.
The first characteristic is an indicia of a first wall side of the product. The second characteristic is an indicia of a second wall side of the product and the third characteristic is an indicia of a wall thickness between the first wall side and the second wall side of the product.
Other objects and advantages will be readily apparent to those skilled in the art upon viewing the drawings and reading the detailed description hereafter.